Most of the train's carriages were empty. The middle four, however, were packed with bank boxes destined for temporary storage in a nearby naval barracks. They contained a fraction of the freshly-minted euros that, on January 1 will replace francs, marks, lire and nine other currencies in the pockets of 300 million European citizens.

The delivery of £400 billion worth of euro notes and coins to banks and companies in the 12-country euro-zone begins next Saturday. The governments hope that the transition will be smooth as well as historic. The criminal fraternity is already making its own preparations.

Across the Continent, trains, security vans and army lorries have been commandeered in preparation for the financial revolution. By the time e-day (as the launch date has been dubbed) arrives, 14.5 billion euro notes and 50 billion euro coins are scheduled to have made the journey to bank safes and shop tills.

"The threat of armed robbery and counterfeiting is the major danger in this transition period," said Derek Porter, the deputy head of the anti-fraud office at Europol, the European Union-wide police body that has set up a special division to oversee the changeover. "We need to be aware of this. A high level of co-ordination between different police forces is going to be needed. The period between now and the disappearance of national currencies is an obvious window of opportunity for criminals."

British counterfeiting gangs are already trying to forge euro banknotes, according to the National Criminal Intelligence Service. "During the initial period, forgeries may be crude, but with time, counterfeiters will almost certainly come up with convincing copies," a spokesman said. The criminal threat is recognised by the Continent's police forces. "I dare not think what would happen if we had a big accident or a terrorist attack in this period," said Bernhaut Witthaut, the president of the German police union.

The location of the euro warehouses across Europe is being kept secret. Most are believed to be on military or naval sites. When deliveries are to be made, euro convoys will leave these depots without warning. Railway station managers will be required to devise a secret "euro timetable" alongside the normal traffic. Many convoys will be monitored by satellite.

A successful hold-up could have implications far beyond the monetary value of the load. Counterfeiters are particularly keen to obtain the actual notes. The chance to forge a currency used by 300 million euro novices will never come again.

The European Central Bank (ECB) has already prepared a "counterfeit guide" which is to be distributed throughout the euro zone. A publicity campaign, also beginning next week, will target the ordinary citizen.

"Everything has been done to make this currency harder to counterfeit than any previous money," said Jean Rodriguez of the ECB who will unveil the notes and coins on Thursday. "The game now is to educate the public about how to distinguish the genuine from the forged." Despite an apparently united front, however, the elaborate security measures put in place mask an alarming level of disagreement over how to do something that has never been done before.

"No one really has any idea how it's going to work out," said one official at the Bank of France. "Everyone has different plans and timetables. France, Belgium, Spain and Portugal will distribute coins to banks and companies from next week. The notes will be delivered later. In Germany, Austria and Luxembourg notes and coins will go out together. In Greece they are waiting until October. In Finland and the Netherlands, they are going to wait until December. Who knows what the best way is?"